MIXTURES AND ELEMENTS DESIRABLE FOR ELECTRICAL WORK.
Castings for electrical work were supplied by our foundry for several years to a leading manufacturer. It was with much surprise that we found, when first commencing this work, that no one in the plant using our castings knew what chemical properties were essential to exist in their dynamos, other than that the buyer wanted them soft, as it was found that a hard metal resisted the action of the current and did not form a good magnetic conductor. To give an idea of what properties are essential in castings for electric work, the following analyses of drillings which were taken from a dynamo casting for the author, which had proven to possess good electrical induction or magnetic permeability, is presented: *
TABLE 58.—CHEMICAL ANALYSIS OF DYNAMO IRON.
Silicon. Sulphur. Phosphorus. Manganese. Graph. Carbon. Comb. Carbon. Total Carbon.
3.190 •075 .890 •350 2.890 .060 2.950
A study of the above analysis will show the product to be a very soft iron, which in a general sense covers the requirements; and when it is said that all elements should be avoided which favor the formation of combined carbon, the founder has a key to guide him in
*For the relative conductivity of different metals for heat and electricity, see Table 135, page 593.ll show a greater chill than from an excessive use of silicon. Then again, the latter will give a very brittle body, while the former will be of a stronger character. It is to be remembered that there is a limit to the use of silicon in affording softness, and that it can make very brittle castings, as shown on page 209.ossessing more of a.50 to 3.00